Endocrine Exam 1 (Rice Insulin)

T/F: insulin is a protein

True

When was fully human insulin first cloned?

1982

When was rapid acting insulin first made?

1996

When was long acting insulin first developed?

2000

When was insulin first used clinically?

1912

T/F: the amino acid sequence of insulin is highly conserved between species, but the c-peptide region can vary significantly

True

T/F: both human and animal insulins can elicit allergic reactions to the insulin molecule

False, it is due to the preservatives or impurities

How many of the 3 disulfide bonds in insulin are intERstrand?

2

How many of the 3 disulfide bonds in insulin are inTRAstrand?

1

The inTRAstand disulfide bonds of insulin occur on which strand?

A chain

C-peptide is removed by PC1 and PC2 at ____ sites

dibasic

The following describes which chain of insulin?

• 21 amino acids long

• Has an inTRAstrand disulfide bond at A6 and A11

• Has 2 alpha helices separated by a loop

A chain

The following describes which chain of insulin?

• 30 amino acids long

• Has 1 alpha helix followed by a turn

• Has 1 beta sheet

B chain

Which is the correct pairing of intERstrand disulfide bonds?

A7-B7 and A20-B19

What is the name of the yeast, also known as brewers yeast, that is used to make recombinant human insulin?

S. Cerevisiae

T/F: bacteria, such as e. coli, are able to fold, proteolytically process and glycosylate proteins they make

False, this is true for eukaryotes such as s. cerevisiae

Which bacteria is used to produce recombinant insulins?

E. coli

Which change to recombinant insulin synthesized in S. Cerevisiae allows for insulin to be secreted from the yeast?

Alpha factor (leading peptide)

Is insulin a homodimer or heterodimer?

Heterodimer

How many amino acids long is human insulin?

51

Activation of alpha 2 receptors _____ insulin secretion and activation of beta 2 receptors _____ insulin secretion

Inhibit, increase

Which describes the resting state (fasting) of beta cells?

HypERpolarized

Which is the rate limiting step of glucose stimulated insulin release?

Phosphorylation of glucose to G6P

Put these events in order

1. Increased intracellular Ca2+ triggers insulin secretion

2. Membrane depolarization opens Ca2+ channel

3. ATP sensitive K+ channel closes, leading to depolarization

4. Glucose enters the cell via GLUT2

5. G6P increases ATP

6. Glucose is phosphorylated by glucokinase to form G6P

4, 6, 5, 3, 2, 1

Increased intracellular Ca2+ trigger….

Insulin secretion from storage vesicles

T/F: only beta cells of the pancreas have insulin receptors

False, nearly all cells have them

How many insulin molecules can 1 insulin receptor bind?

4

Binding of insulin to the insulin receptor triggers which to translocate to the cell membrane and begin importing glucose?

GLUT4

The insulin receptor ______ when insulin binds

is phosphorylated and begins intracellular signaling

In both storage vessels and in the blood, at concentrations lower than 0.1 mM, insulin is ______. Above 0.1 mM it is found as _____.

a monomer, dimers or hexamers

Which links insulin monomers into hexamers?

Zinc

Which form of insulin binds to the receptor?

Monomer

Which region of insulin is NOT critical for insulin binding to the receptor and thus is frequently modified to achieve different kinetic profiles?

B27-30

Why are phosphate buffers added to insulin formulations?

To prevent the formation of fibrils

Why is albumin added to insulin formulations?

To prevent absorption of insulin to tubing

Why does insulin glargine have a gly substituted for A21 asn?

To prevent the deamidation of it at pH 4

At neutral pH, B3 Asn can be deamidated which leads to what?

Immune response

T/F: all insulin formations containing zinc appear cloudy

False, formulations containing protamine do

Why is protamine added to insulin formulations?

It causes insulin to crystallize, which prolongs its action

What is protamine’s charge?

Positive

Which was the first insulin analog created?

Humalog

Which analogue is made in yeast?

Novolog

Which analogue is modeled after IGF-1?

Humalog

Glulisine

B3 Asn → Lys and B29 Lys → Glu

Glargine has two arg added to the end of the B chain and A21 apn →gly, what purpose do they serve?

Increase isoelectric point to make the insulin more soluble in acidic pH and less soluble at physiologic pH to increase duration of action

Out of these two forms of insulin glargine, which has fewer nocturnal hypOglycemic events?

Toujeo

How does degludec insulin prolong its action?

Via formations of a SQ depot